What would happen if the speed of light was infinite?

Answer 1

technically the speed of light is not infinite. but passing the speed of light means

that you would travel backwards in time. so if the speed of light is infinite, then

the years that passed will get brighter and brighter. So ancient times would be

burned to crisp while the future would be dim. the concept here is that light dims

as the farther you travel forward in time. that is because all the light is past the

spped of light so they travel backwards in time.

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Thinking in terms of a few things that are the way they are today because of the

finite speed of light, this becomes a fascinating question to ponder. For almost all

of human history, until only the most recent few moments, it made no difference.

But I can think of a few modern cases where it does:

-- Radio communication.

Radio, TV, cellular, GPS etc. all become much more reliable, as 'multipath' fading

ceases to exist. Multipath fading is attenuation arising from the phase difference

between the direct and the reflected signal, due to the difference in transit time

over paths of different lengths. With infinite propagation speed, there is no delay

over a longer path, so no phase difference at the receiver. All rays add !

-- Stars no longer 'twinkle'.

Scintillation of an optical point source is exactly the same multipath fading from

the radio world.

-- Laser holography . . . not possible.

-- Directional antennas ... Yagis, ham beams, log periodics, AM tower arrays, any

'parasitic'

structure ... are no longer directional. But I think parabolic reflectors still work.

-- Fermat's Principle ... which I no longer understand ... involving, as it does, the speed

of light, is out the window. The laws of reflection and refraction don't depend on Fermat,

but they can be derived from it. Since it no longer holds, you don't suppose . . .

-- Young's experiment, coherence, interference from thin films, Michelson's interferometer,

diffraction, Bragg's Law . . . all gone.

-- GPS can't exist ! At least not the way it operates now. The device in your hand

or in your car compares the different lengths of time it takes for the GPS signals to

reach you over the different distances from several satellites in different places. If

the speed of light (and radio) is infinite, then it makes no difference where you are

or where the satellites are. It takes no time for any signal to reach you from any bird.

-- And if the speed of light is infinite in all media ! ! . . . no refraction. Goodby to Snell,

lenses don't work, spearing fish is no problem as long as you're not severely myopic, and

the pencil still looks straight when half of it is under water.

-- Woo hoo ! You MUST be myopic ! Just like everybody else in the world. MAYBE

you can form a workable visual image of an object at infinity, by stopping your pupils

down to pinholes, I don't know. But for nearby objects, forget it ! The cornea, the lens,

the humors, nothing can help your focus.

-- Driving: Police radar still detects your car, but I think the Doppler shift is gone,

so your speed can't be measured with it.

-- Same for Doppler weather radar. It has no advantage over older radar. It tells you

that a thunderstorm cell is right there, but it can't tell you anything about winds or

rotation inside the cell.

-- Oops. Sorry. Radar doesn't work too well at all. It can still tell you the direction

to the target, because that's the direction where you send a burst and some of it

comes back. But it can't tell you the distance to the target, because the echo

returns from a near target or a far target at the same time.

In fact, maybe the whole echo-detection scheme can't actually be implemented in

hardware, because echoes return in zero time, before you've ever had a chance to

turn off your burst transmitter and listen for the echo.

-- Which brings us to Astronomy and Cosmology: We can see the status of every

object in the universe that's bright enough for us to detect, right now. We can't

see the evolution or distribution of galaxies in the early universe ... no "looking

backward in time". No red shift, no blue shift, so we can't detect radial speeds,

and we lose most or all of the overwhelming body of data that's explained now by

the concept of the "expansion" of the universe.

-- Relativistic effects: As mind-bending as this is under 'normal' circumstances, it's

more so if we imagine a fundamental change in the nature of light.

. . . We know right away that speed no longer affects mass, and that the Lorentz contraction

and time dilation both go away, because no matter how fast you move, v2/c2 is always zero.

. . . It becomes a lot easier now to accelerate your car or your spaceship all the way

to 3 x 108 meters per second, but now, that's still 0% of the speed of light !

. . . Photons can now have rest-mass if they want it. And if they don't then their mass

is still zero when they're whizzing about.

. . . But then, how can photons carry energy ?

. . . Does that mean that E = mc2 goes away ? Well phoo, I guess it had to anyway,

as soon as 'c' became infinite.

Those are the first few minor consequences of infinite light speed that I can think of just now.